فصلنامه زمین شناسی اقتصادی
سال سیزدهم شماره 3 (پیاپی 30، پاییز 1400)

About 75% of world copper, 50% of molybdenum, and 20% of gold are produced from porphyry copper deposits (Sillitoe, 2010) with an average ore grade of 0.45–1.5% Cu, 0.007–0.04% Mo and up to 1.5 ppm Au. Porphyry copper deposits are commonly associated with intermediate composition arc-related igneous rocks with high Sr/Y and La/Yb ratios (Richards, 2011). Igneous rocks having ratios of Sr/ Y > 25 and Y < 10 ppm are considered adakitic type.The aim of this work is to modify the name of Urumieh-Dokhtar magmatic belt (UDMB), petrological studies of granitoids from Saveh to Jiroft, determination of the genetic relationship between porphyry copper deposits and adakitic and non-adakitic granitoids, and comparison of Miocene-Pliocene adakitic volcanic rock in different parts of Iran with barren adakitic granitoids. The role of a thermal gradient, depth of dehydration, water content, source rock, partial melting percentage, and oxygen fugacity in the formation or non-formation of mineralization, grade, and reserve of porphyry copper deposits are also investigated.

The information used can be divided into three parts: 1) data related to I-type magnetite series granitoids related to porphyry copper deposits of Miocene age in Saveh-Nain-Jiroft magmatic belt (SNJMB) which in Table 2 are presented, 2) data related to barren I-type magnetite series granitoids of Miocene age of SNJBM are reported in Table 3. In addition, radiogenic isotope information of barren and fertile SNJMB granitoids and volcanic rocks is presented in Table 4. 3) Information related to Miocene-Pliocene adakitic volcanic rocks, which is shown in Table 5.

Granitoids show the characteristics of subduction zone magmas. So that the enrichment of LILE elements and the depletion of HFSE elements can be seen. Also, enrichment of LILE elements and depletion of HFSE elements of fertile granitoids is more than barren units. Dalli deposit samples show a moderate pattern between barren and fertile granitoids (Fig. 3). All the evidence presented shows that all granitoids are I-type and magnetite series.In the fertile granitoids, the ratio of (La/Yb)n is between 15 and 38. However, this is between 2 and 14 (mostly below 10) in barren granitoids (Tables 2 and 3, Figs. 5A and 5B). Negative anomalous values ​​of Eu are seen in Miocene barren granitoids (Eu /Eu* value between 0.43 and 1 with an average of 0.65) (Table 3). While fertile granitoids have positive to slightly negative Eu anomalies (Eu / Eu* value between 0.82 and 1.3 with an average of 1.2).The initial values of 87Sr/86Sr of Miocene fertile granitoids vary between 0.704253 and 0.704702; while in barren granitoids, it is between 0.705 and 0.7085. Fertile Miocene granitoids have positive εNd (i) (0.29 to 3.39 mean 2.15) and in barren units is between 3- and 2.6 (Table 4).The value of the ratio (La/Yb)n of all volcanic units is between 13 and 78 and mostly above 20. They have positive to slightly negative Eu anomalies (Eu/Eu * values between 0.89 and 1.72) (Table 5). Figure 9 shows the fertile granitoids of the SNJMB similar to adakite volcanic rocks are located in the adakite field. In addition, Figure 11 show that all samples are high silica adakitic type. However, barren granitoids, which are mainly located between Saveh and Nain, are non-adakitic and are plotted within the normal arc range (Fig. 

In this paper, the name of UDMB was changed to Saveh-Nain-Jiroft magmatic belt (SNJMB) based on the evidence of lack of magmatism between Saveh to the extent of Takab and absence of air magnet anomaly. Magmatism of Urumieh to Takab is a continuation of the western Alborz magmatic belt. Based on the characteristics of magmatism and mineralization, SNJMB can be divided into two distinct belts: 1) Saveh-Nain Magmatic Belt (SNMB), which mainly consists of non-adakitic barren I-type magnetic granitoids. Based on the ratio (La/Yb)n, these granitoids originate from a depth of 60 to 80 km, and a mantle wedge and based on the amount of Eu/Eu*, conditions were oxidant. The initial 87Sr / 86Sr ratio indicates that they had a lot of contamination with the continental crust. The crustal thickness in SNMB is less than 48 km, 2) Nain-Jiroft Magmatic Belt (NJMB) which hosts porphyry copper deposits. The Miocene granitoids of this belt are magnetite series and I-type adakite. Based on the ratio (La/Yb)n, these granitoids originate from the depth of garnet stability (more than 90 km) and partial melting of slabs and are based on Eu/Eu* Oxidizing conditions have been established at the place of origin. The initial 87Sr / 86Sr ratio indicates slight contamination with the continental crust. The crustal thickness in NJMB is 48 to more than 52 km.Geochemically, adakitic volcanic rocks are similar to the fertile adakitic granitoids of NJMB, but these units do not contain any mineralization. The characteristics of the oceanic slabs of Neo-Tethys varied considerably during the SNJMB, leading to various magmatism and mineralization. The thermal gradient, depth of dehydration, amount of water, source rock, and the percentage of partial melting along the belt control the type of magmatism and the formation of mineralization. Note Figure 15.

Fe skarn deposits are the largest skarn deposits which are exploited for Fe as well as by-products of Cu, Co, Ni and Au (Meinert et al., 2005). They are one of the most important Fe deposits in the Zanjan province which have been exploited in recent years. The Alamkandi Fe deposit is one of these Fe skarn deposits which is located at 35 km west of the Mahneshan within the Takab-Takht-e-Soleyman subzone, northern Sanandaj- Sirjan zone. In this area, alternation of amphibolite, amphibole schist and biotite schist with intercalations of marble belonging to Paleozoic and intruded by late Oligocene alamkandi granitoid exist. This intrusion has caused contact metamorphism and formation of Fe mineralization. Some of the Fe skarn deposits in the Zanjan province were studied during the past years (i.e., Nabatian et al., 2017; Mokhtari et al., 2019) and valuable information is present about their geological and mineralization characteristics. However, the Alamkandi granitoid and Fe deposit have not been studied until the present. In this research study, geochemistry and petrogenesis of the Alamhandi granitoid along with mineralogy, textures and geochemistry of Fe deposit and thermodynamic conditions for formation of contact metamorphic rocks have been studied.

This research can be divided into two parts including field and laboratory studies. Field studies include recognition of different parts of granitoid intrusion and skarn aureole along with sampling for laboratory studies. During field work, 65 samples were selected for petrographic and analytical studies. 19 thin sections and 13 polished thin sections were used for petrographical and mineralogical studies. For geochemical studies, 15 samples from granitoid and ore skarn sub-zone were analyzed by XRF and ICP-MS methods at the Zarazma laboratory, Tehran, Iran. 
  

Based on petrographic studies, the Alamkandi granitoid is composed of granodiorite, quartz diorite and porphyritic diorite. Granodiorites with hetrogranular texture are composed of plagioclase, quartz, K-feldspar, hornblende and biotite. Quartz diorites indicate porphyroid to seriate and hetrogranular textures and are composed of plagioclase, clinopyroxene, hornblende and quartz. Porphyritic diorites have porphyritic texture with plagioclase and amphiboles phenocrysts. The Alamkandi granitoids demonstrate calc-alkaline to high-K calc-alkaline affinity and can be classified as metaluminous I-type granitoids. Primitive mantle-normalized (McDonough and Sun, 1995) trace elements patterns for the Alamkandi granitoids indicate LILE and LREE enrichment along with negative HFSE anomalies and positive Pb anomaly. Chondrite-normalized (McDonough and Sun, 1995) REE patterns for these rocks demonstrate LREE enrichment (high LREE/HREE ratio). Based on tectonic setting discrimination diagrams, the Alamkandi granitoids were formed in the active continental margin.Fe mineralization in the Alamkandi area crops out in discrete places as massive and lens-shaped bodies. The Northern outcrop body has 150m length and up to 50m width, while the southern outcrop body has 100m length and up to 20m width.  Microscopic studies reveal that the skarn zone at the Alamkandi granitoid is composed of garnet skarn, pyroxene skarn, epidote pyroxene skarn, serpentine skarn, and ore skarn sub-zones. Magnetite is the main ore mineral along with some pyrite and chalcopyrite. Garnet, clinopyroxene, olivine, serpentine, epidote, actinolite, calcite and quartz are present as gangue minerals. Based on the field and microscopic studies, the Alamkandi Fe deposit has massive, banded, disseminated, brecciated, vein-veinlets, replacement and relict textures. Based on mineralogical and textural studies, the skarnization processes in the Alamkandi deposit can be divided into 3 stages including: (1) isochemical metamorphic stage, (2) prograde metasomatic stage and (3) retrograde metasomatic stage.

Based on skarn mineralogy, the XCO2 vs. T and T vs. logƒO2 diagrams were used to determine the possible physio-chemical conditions. According to these diagrams and considering mineralogical and textural evidence, maximum temperature for formation of olivine in XCO2≈0.1 and P=1kb was about 450-600°C. Furthermore, garnet and clinopyroxene were formed simultaneously at 430-550°C and ƒO2 equal 10-18 to 10-22. In temperatures less than 450°C, olivine was replaced by serpentine while in temperatures less than 430°C and increasing ƒO2, garnet and clinopyroxene were replaced by epidote + quartz + calcite and actinolite + quartz + calcite, respectively. In temperatures less than 430°C, fluids in equilibrium with granitic intrusion and with relatively high sulfidation (ƒS2>10-6), were not in equilibrium with andradite. Therefore, andradite was replaced with quartz + calcite + pyrite. With reducing ƒS2 (<10-6), andradite was replaced by quartz + calcite + magnetite. During the early retrograde stage, magnetite and pyrite were formed along with quartz and calcite. Mineralogical studies indicate that pyrite was formed after magnetite. In this regard, it seems that metasomatic fluids probably had ƒS2≈10-6.5 and less than 430°C temperature in the beginning of the retrograde stage. Presence of hematite lamella within the magnetite demonstrates that ƒO2 was probably about 10-22 in the beginning of retrograde stage.

Erosion and oxidation of massive sulfides when uplifted and exposed to the surface, commonly lead to the formation of gossans. In this process, surface water will dissolve soluble elements, and oxides and hydroxides of iron (goethite and hematite) will form on top of the volcanogenic massive sulfide (VMS) deposits. The main tectonic settings for Iranian VMS deposits are magmatic arcs, which can be subdivided into volcanic primitive arc, arc/intra-arc rift, and back-arc settings and Sanandaj-Sirjan zone is one of the structural zones that host many VMS deposits in Iran (Mousivand et al., 2018).The study area is located southwest of Jiroft, Kerman province. The main rock units include vitric tuff, pelagic sediments, volcano-sedimentary rocks, gabbro and intermediate to mafic dykes. Mineralization has occurred in volcano-sedimentary beds. The pelagic sediments which are composed of limestone, shale, sandstone, siltstone and interlayers of pillow lava, are the main hosts for mineralization. Surface oxidation of mineralized zones has led to conversion of primary sulfides to iron oxides and hydroxides to form gossan. This study contributes to mineralogical and geochemical composition and mineralization of gossans to demonstrate how surface oxidation of primary sulfides can play a role in locating VMS mineralization at depth.

A geological map with a scale of 1:5000 was prepared during field and laboratory studies. Twenty polished section were studied to identify mineral distributions and textures, and some of them were chosen for scanning electron microscopic (SEM) examinations. Fifteen rock samples from the gossan horizons were chosen for geochemical studies. The samples were taken from across the mineralized horizon. Six rock samples were taken from old mining site outcrops to compare the geochemistry of gossans with other surface mineralization. All samples were sent to the laboratory for analysis by Inductively Coupled Plasma Atomic Emission Spectroscopy (ICP-AES). The rare earth element (REEs) values were measured by Inductively Coupled Plasma Mass Spectrometry (ICP-MS). X-ray diffraction (XRD) spectroscopy was used to identify mineralogy of 30 rock samples. All analyses were performed in the central laboratory of the Geological Survey and Mineral Exploration of Iran, in Tehran and Karaj.

The ore and gangue minerals have massive, layered, disseminated, veinlet, breccia and replacement textures. Based on mineralography, XRD and SEM studies, the main minerals are hematite, goethite, quartz, and jarosite-group minerals. The upper horizon of gossan, with 13 meters thickness has large volume of hematite and gothite minerals. The enrichment of gold, arsenic, antimony, silver, lead and bismuth were observed in this zone. The lower horizon, with a thickness of about 1.5 meters show anomalies of copper and zinc elements. The highest amount of gold and silver were measured about 18.5 and 120 g/ton, respectively. The highest amount of lead element is 1.3 wt.%, which shows a positive correlation with silver variations. The other values are copper 0.16 wt.%, arsenic 0.61 wt.%, bismuth 580 g/ton, and antimony 280 g/ton.

Trace and REEs geochemistry are useful in identifying gossans and probable sources (Scott et al., 2001). Geochemical studies also can be used to separate mature from immature gossans. Although the composition of gossans is influenced by early composition of the ore, gossans with high content of Pb (more than 4 wt.%) are usually considered immature. The average Pb measured in the studied gossans is about 2210 g/ton. The Ag content is also low (less than 150 g/ton) and there is a relatively linear relationship between increasing Ag and Pb content. High values of copper often refer to a lower degree of maturity. In the studied gossans, the average amount of Cu is about 2900 g/ton, which is much lower than the immature gossans with average 1.6 wt.%. Therefore, the results of chemical analysis indicate that these gossans are in the category of mature ore bearing gossan.The REE from La to Lu, is relatively consistent with the shape of REE profiles for volcanogenic massive sulfide mineralization and concurrent massive sulfide gossans (Peter et al., 2003; Volesky et al., 2017; Gieré, 1993). The pattern of distribution of REEs shows small positive Eu enrichment and zoning of precious mineral elements confirms the possibility of orebody under the gossans. Further exploration of volcanoge

The study area is located in the Eastern Alborz zone (Gansser, 1951) which is a part of the northern margin of Gondwana during the Paleozoic (Stöcklin, 1974; Salehi Rad, 1979; Berberian and King, 1981; Şengor, 1990; Alavi, 1991, 1996; Stampfli and Borel, 2002; Allen et al., 2003; Horton et al., 2008; Sinha, 2012, 2013). According to studies conducted by Gansser (1951) and Hubber (1957), the gabbro masses of South Gorgan (Nahar Khuran Valley) belong to the ophiolite collection. Meanwhile, 6km South-East of Galougah city, Gorgan schists have been covered by underlying Jurassic sandstones with s steep discontinuity. The parts resulting from the erosion of Gorgan schists were observed in the sequence conglomerate of the underlying Jurassic. At the beginning of the Ziarat Valley, about 800 meters above the Nahar Khuran, two small tectonic masses (the thickness of about 11 meters) are placed on the layers. These masses are mostly metamorphic. The metamorphic rocks (Gorgan schists), as one of the important geological units in Iran, are mainly formed from low-metamorphic rocks such as slate, phyllite, chlorite schist, greenschist and micaschist along with volcanic rocks and gabbrodiorite masses infiltrating them.

To prepare a geological map of the study area, field sampling and fieldwork were first done from the various units in the region. Over 100 samples were collected from the area. Approximately 70 thin cross-sectional samples of the tectonic rocks of the area were selected from them and investigated using a polarizing microscope. In this paper, 11 points of clinopyroxene were selected for microprobe analysis. The point analysis done on these minerals was conducted using the EPMA method using a microprobe analysis set in the Center of Mineral Processing of Iran (Karaj). The structural formula is calculated using the Excel (Spreadsheet) and dividing them was done by the MinPet 2.02 software package. Given that microprobe analysis is unable to distinguish Fe2+ and Fe3+ and given that it reports total iron as FeO*, it is necessary to separate these two from each other in order to calculate the minerals’ structural formula.

Petrographic studies identified rocks including gabbro, olivine gabbro, monzonite, gabbro to monzogabbro altered, metagabbro, and catalactic porphyry diorite. Mineralogically, these rocks consist of phenocrysts of plagioclase with labradorite composition, clinopyroxene and olivine with accessory minerals of apatite, sphene, biotite, and metal minerals. Secondary minerals are chlorite, sericite, clay mineral and epidote. The dominant textures in these rocks are granular and ophitic. The results of electron microprobe analysis of these clinopyroxenes show that they have augite compositions. In addition, gabbros also mostly show alkaline composition.

To precisely investigate the rocks in the research area, the results of the chemical analyses of minerals were used in determining their petrogenesis. Felsic minerals mainly include altered plagioclase, the main combination of which is labradorite and which is converted to the secondary albite due to hydrothermal alteration processes. The combination of clinopyroxenes available in the volcanic rocks is in Quad range and has a composition of augite. The temperature calculated for the clinopyroxenes in gabbros is 1277.7 to 1353.1°C and the pressure is more than 10 Kbars.  (On the baseline of 3.65kbar per 1km in depth), the formation of clinopyroxenes in the parent magma was over 37km. The primary water content of the gabbro magmas is estimated to have been between 0.5 and 5 wt.%. Distribution of aluminum in tetra and octa positions of clinopyroxenes depends on pressure and the amount of water available in the crystallization environment. Accordingly, the amount of AlIV decreases as the amount of water increases. Tectonomagmatic diagrams suggest that the host rocks are alkaline and are related to volcanic arc setting.

The studied area is situated 15 km away from the southwest of Maimeh at the western part of Urumieh-Dokhtar magmatic arc. This zone is a part of the Zagros orogenic belt formed due to the subduction of the Neo-Tethyan oceanic crust under the Central Iran block. The magmatic activity in the Urumieh-Dokhtar magmatic arc has begun in Eocene (Alavi, 2004) and continued until Quaternary (Ghasemi and Talbot, 2006). In the middle part of the studied area, several outcrops of the post-Early Cretaceous volcanic rocks with basaltic to andesitic composition have been seen (Vahdati Daneshmand, 2006). Until now, no petrological and geochemical data about these rocks are present. Therefore, in this study, petrographic and the geochemical features of these rocks are discussed in detail. This study aims to reveal a better understanding of the petrology and petrogenesis of volcanic rocks in the southeast of Maimeh and the middle part of the Urumieh-Dokhtar magmatic arc as a part of the Zagros orogenic belt.

To reach the goal of the research, after collecting basic information using geological maps and works done in the study area, all volcanic outcrops systematically sampled, and more than 50 fresh samples were chosen and studied. Afterward, seven samples were chosen for geochemical analyses by using inductively coupled plasma mass spectrometry (ICP-MS) at the ACME Laboratories, Vancouver, Canada. The results of chemical analyses are listed in table 1.

Based on the field observations, the volcanic rocks have basaltic to andesitic composition with plagioclase, clinopyroxene, olivine, amphibole, biotite, and opaque microphenocrysts. Clinopyroxene (probably augite) is the main minerals as phenocrysts and small mineral in the groundmass. Olivine phenocryst has undergone limited alteration to iddingsite and amphiboles show burned margin. Opacitization in amphibole occurs due to a decrease in water pressure with magma rising or as a result of the increase in temperature (Plechov et al., 2008). These rocks have microlithic porphyry, glomeroporphyry and vesicular textures. According to geochemical analysis, intermediate rocks have calc-alkaline nature and basalt is alkaline. They display enrichment in LILEs (Rb, Ba, K, Sr, U, and Th) relative to HFSEs (especially Nb, Ti, and P) and coherent REE patterns characterized by enrichment in LREEs relative to HREEs without negative Eu anomaly. These features are characteristics of subduction-related magmatism (Woodhead et al., 1993). U and Th enrichment may be due to crustal contamination (Kuscu and Geneli, 2010) or the addition of pelagic sediments and/or altered oceanic crust to the source of magma (Fan et al., 2003). The tectonic discrimination diagrams show an active continental arc setting for these rocks. Geochemical evidence shows that the volcanic rocks were originated from low degree partial melting (<0.1) of the enriched mantle with Cpx- garnet lherzolitic composition in 80 km depth. Mantle enrichment is due to the addition of aqueous fluids derived from dehydration of the subducted oceanic crust. It seems that the continuous subduction of cooled oceanic crust into the mantle along with convergence between Arabia and Central Iran plates led to low degree partial melting of the mantle and producing alkaline magmas. The ascending parental magma was differentiated and undergone AFC processes until rising from the crust. In these processes, the alkaline basalt under the influence of fractional crystallization and crustal contamination turned into intermediate compositions of calc-alkaline andesite. It seems that these rocks were formed from the subduction of Neo-Tethyan oceanic crust under the Iranian microplate in an arc magmatic zone.

The post-Early Cretaceous volcanic rocks in the southeast of Maimeh is situated in the western part of Urumied-Dokhtar magmatic arc and includes most basic to intermediate associations. The rocks have the porphyritic texture with basalt to andesite composition and are characterized by alkaline to calc-alkaline affinity and enrichment in LIL elements (Rb, Ba, Th, U and …) relative to HFSE with negative Ti and Nb anomalies and highly differentiated pattern of rare earth elements, as evident in spider diagrams normalized to primitive mantle and chondrite. The significant features are mainly a result of subduction-related magmatism. Tectonomagmatic diagrams suggest an arc-related tectonic setting for these rocks. Based on the geochemical evidence, the volcanic rocks originated from low degrees (>1) partial melting of a garnet- lherzolitic mantle source that enriched by slab-derived fluids. The magma has undergone AFC processes during ascending and alkaline affinity changed to calc-alkaline nature. The volcanic rocks occurred as a result of the subduction of the Neo-Tethyan oceanic crust beneath the Central Iran microplate.

The Gaz Boland area is located in the northwest of Shahr-e-Babak city within the southern extension of the Urumieh-Dokhtar magmatic arc. The extended convergence history of the Neo-Tethys Ocean between Arabia and Eurasia (from ∼150 to 0 Ma) comprised of a long-lasting period of subduction followed by continental collision during the Tertiary (Omrani et al., 2008). Following the collision, volcanism continued dramatically in some parts of the Urumieh-Dokhtar volcanic-plutonic belt, such as Pleistocene basic volcanism in the Shahr-e-Babak area in western Kerman. Thus, Neogene basalts in the Gaz Boland area in Kerman are known as the last magmatic activity of this part of Iran.

Ten samples of volcanic rocks were selected for geochemical analyses. All samples were analyzed for major elements by X-ray fluorescent (XRF) and trace elements using Inductively Coupled Plasma Mass Spectrometry (ICP-MS), in the Kansaran Binaloud Co., Iran. The results of the analyses were evaluated using the GCDKIT software package.

Plio‐Pleistocene basaltic rocks are the youngest volcanic activity in the Gaz Boland area. The main texture of these rocks is porphyric with microlithic form and they contain major minerals of olivine, clinopyroxene, and plagioclase. Based on geochemical data, the volcanic rocks of the Gaz Boland region have been derived from a calc-alkaline magma. Moreover, examination of trace element diagrams of these lavas indicates that magma is related to the subduction zone and active continental margin. Based on various elemental ratios and diagrams, the volcanic rock-forming magma in the Gaz Boland area have been derived from the asthenospheric mantle deep in the subduction zone. The source rock composition of these basalts is garnet-bearing lherzolite, which has been slightly enriched during the subduction process by fluids originating from the subducting oceanic crust. The rock-forming magma was also contaminated by the continental crust during the ascent and has endured the AFC process.

The Gaz Boland calc-alkaline basalts show enrichment in LILE, LREE, Th, and U, but depletion in HFSE (Ta, Ti, and Hf) and HREE. These rocks show characteristics of subduction-related (active) continental margin tectonic environments. According to the Sm vs. Sm/Yb diagram (Aldanmaz et al., 2000), the Gaz Boland samples were plotted in the partial melting range of about 10 to 15% of a garnet-rich lherzolite source. Asthenospheric mantle-derived magmas have Nb/La ratios > 1 or La/Nb ≈ 0.7. A low Nb/La ratio (<0.5) indicates lithospheric mantle and high Nb/La ratio (>1) indicates asthenospheric mantle (Smith et al., 1999). On the other hand, lithospheric mantle-dependent magmas have a La/Nb ratio greater than 1, whereas, in asthenospheric mantle-derived magmas, it is about 0.7 (DePaolo and Daley, 2000). In volcanic rocks of the study area, La/Nb and Nb/La ratios are 0.2 to 0.7 and 1.5 to 4.8, respectively. In addition, volcanic arcs can be classified into highly enriched and poorly enriched categories based on Ce/Yb ratios. Enriched arcs are defined as having Ce/Yb >15 (Hawkesworth et al., 1991; Juteau and Maury 1997). The mean Ce/Yb of the Gaz Boland rocks is 9.7 which defines a poorly enriched arc signature. Certain chemical parameters can be used to assess the degree of contamination. For example, basaltic rocks affected by crustal contamination exhibit La/Ta ratios > 22 (Abdel-Rahman and Nassar, 2004) and Nb/Th ratios < 5 (Condie, 2003). The values of such elemental ratios in the Gaz Boland basalts are 18 to 64 and 3 to 5, respectively (Table 1), which suggest that the magma was subjected to crustal contamination.

The Malayer-Esfahan metallogenic belt is one of the main Zn-Pb mineral regions of Iran which is in the central part of the Sanandaj-Sirjan zone (Rajabi et al., 2012). The Sanandaj-Sirjan zone has long-lived magmatism and deformation related to the Mesozoic subduction and the middle Miocene collision. The rocks in this zone are the most highly deformed ones in the Zagros orogen (Mohajjel and Fergusson, 2014). Most of the sediment-hosted Zn-Pb deposits of the Malayer-Esfahan metallogenic belt are hosted within extensive Early Cretaceous platform carbonates deposited during an extensional back-arc basin (Rajabi et al., 2012). As the Zn-Pb deposits were initially formed in an extensional setting, subsequent compressional phases of the Eurasian and Arabian continental collision have deformed these deposits. It is the inversion tectonic phase that has played an important role in the evolution of the orogenic belts (Zanchi et al., 2006). In this study, the role of fault systems especially the inverted faults in the Takiyeh Mine has been studied. This mine is located in the NW part of the Malayer-Esfahan metallogenic belt, close to the Takiyeh village.

In this study, faults of the area were distinguished using orthotropic images to investigate the relationship between tectonic structures and mineralization in the Takiyeh Zn-Pb mine. Geometry and kinematics of these faults have been studied during several field observations. Then, the study of polished sections, Zn-Pb analysis from all sections of the mine and XRF and XRD methods have been done for ore mineralization.

The Zn-Pb mineralization in the Takiyeh mine occurs in the Ksl ore-bearing unit of the Lower Cretaceous. The Kl unit is thrusted over the Ksl unit during the compressional phases of the continental collision between the Arabian-Eurasian plates. Mineralization is composed of mineral veins of several centimeters to several meters along the main faults of the study area. Generally speaking, two systems of faults with NE-SW and NW-SE trends have caused deformation and controlled mineralization in the Takiyeh mine. The faults with NE-SW trend cut the NW-SE trend faults, indicating activation of the NE-SW faults in a new stress field. The main fault trends of the study area are most frequent in the N60W and N30E to N50E trends. The dip angle of the NW-SE trend faults generally change between 60 to 70 degrees toward the northeast. These faults are generally steep reverse faults due to the fault plane indicators such as direction of roughness and softness of fault surface. The dip angle of the NW-SE trend faults are generally toward the SW and these fault are exposed as steep fault zones. The SC fabric in these faults indicates reversed and steep movement, causing displacement of the NW-SE mineral veins.Generally, mineralization in the Takiyeh mine has been formed during the Lower Cretaceous extensional phases. So, this region had experienced the extensional regime and normal faults have controlled the upward migration of the hydrothermal fluids and mineralization. Mineralization in the study area is hosted by the Lower Cretaceous unit (Ksl). It is noteworthy that the formation of Zn-Pb mineralization in an extensional setting and subsequent compressional orogeny phases, especially the middle and upper Cretaceous orogeny phases, such as the Laramide orogeny phase, has affected the area under compressional settings. Thus, the inversion tectonic in the study area inverted the low-angle normal faults to steep reverse faults. Generally, inversion tectonic is a common process in regions of continental collisional involving the reactivation of major extensional normal faults as reverse faults. Inversion of a normal fault causes deformation transfer to the fault footwall via shortcut thrusts. The outcrop of some shortcut thrusts in the western part of the Takiyeh mine are evidences of inversion tectonic in the study area. These shortcut faults with NW-SE trend and dip angle toward NE have caused deformation of the Cretaceous calcareous units. In fact, these reverse shortcut faults have been normal faults that formed initially under the Cretaceous extensional regimes and then they became inverted under later compressional phases. The inversion tectonics in the study area, in addition to the formation of shortcut thrusts, has deformed the Ksl unit and steep reverse fault and folding has been formed by progressive deformation. The folded structures in the study area in ductile shaly units have been formed as small Z-shaped folds between fault shear zones. Although these folded structures have been formed between parallel fault zones, several minor faults older than these folds are exposed in some parts of the study area due to the activity of these faults. These older faults have been previously formed between the Ksl unit and were folds during the progressive stages of the inversion tectonic.

The Kushk-e-Bahram Manto type copper deposit is located in the central Iran zone and   is Uremia-Dokhtar Magmatic Arc (UDMA) belt which includes copper porphyry deposits and related mineralization types, including the Manto type copper deposits (Jebeli et al., 2018a, b). Based on the type of mineralization and the presence of sulfides, high electrical conductivity (low electrical resistivity) can be detect in this deposit such as the Manto type deposits (Mehrnia, 2013., Mehrnia, 2016., Teymoorian Motlagh et al., 2012). On the other hand, Induced Polarization (IP) and electrical resistivity (RS) were used in the Kushk-e-Bahram deposit.

The relationship between geoelectrical parameters and the mineralization process were recognized in geophysical assessments of the Kushk-e-Bahram de posit. It is necessary to obtain information about the shape and distribution of the orebody. According to exploratory data of the Kushk-e-Bahram deposit (Jebeli et al., 2018a, b), Cu mineralization has been extended. Therefore, the location and number of geoelectrical profiles were selected, based on previous studies which was generated in the ArcGIS software. The exchanges in the RS and IP values were measured, along three profiles (P1, P2, P3) and Dipole-Dipole arrangement with electrode distance of 10 meters. The device type used is WDJD-3 and 1620 harvest points were surveyed. IP–RS profiles with azimuth 30 to 40 degrees were used in order to identify mineralization areas based on the highest variability of conductivity and load-bearing properties.  Moreover, they were designed and surveyed perpendicular to the mineralization process of the area. Considerations were taken into account based on the location of trenches and the mineralization sequence of this area. The P1 and P2 profiles with an approximate length of one kilometer and P3 profile with an approximate length of 370 m were designed and harvested under a 30 degree azimuth.

In this research study, a number of geoelectrical sections were selected and their surface changes in a two-dimensional environment were refined and internalized by the algorithm used in the diffraction-distance distribution function. According to the position of P1 and P2 profiles, all three quantities of RS, IP and self-Potential have been interpolated to match the alteration zones and faults of the study area in the P3. The quantity of Spontaneous Potential (SP) is not measured and it just suffices to internalize specific electrical changes and IP and their conformity with the effects of alteration and faults in the region. Interpolation of geo-electrical data by the inverse distance weighting estimation method and nearest neighborhood algorithms were carried out (Mehrnia, 2016; Teymoorian Motlagh et al., 2012).Based on the fractal dimension, four targets around the P1 and P2 profiles and eight priorities have been identified around the P3 profile. Based on the results, geo-electrical data distribution pattern was obtained using diffraction-distance model and changes in the fractal dimension of electrical resistivity, induced polarization and self-generating electric potential according to the differences of the fractal dimensions for IP, RS and SP in the Kushk-e-Bahram deposit. It is necessary to interpret geo-electrical sections based on fractal dimension exchanges to avoid the oblique error caused by the fitting of disproportionate quantities as much as possible. Consequently, exchanges in the level of electrical resistivity and induced polarization were calculated. There is no corresponding trend along P1 and P2 profiles. Thus, the results of the diffraction-distance model were correlated with mineralization potential in the depth of the deposit. Continuation of exploration activities (detailed phase) along the P1, P2 and P3 profiles are suggested. Based on inferring from the  Brownian mechanism distribution of electrical resistivity quantities and inductive polarization, priority of P1 and P2 profiles with vein and disseminated mineralization in P3 profile is obtained.